The process of selecting a portion of a photograph for enlargement is known as cropping. The selected portion is typically enlarged to a standard size, for example, eight by ten inches. Generally, the selected portion must be proportioned the same as the desired size of the enlargement. The term proportion refers to the ratio of the length of the enlargement or selected portion to its width. Thus, an eight by ten inch enlargement can be made from various sized selected portions such as four by five, two by two-and-a half, etc.
It is well known to crop a photograph with two individual L-shaped sheets which can be positioned relative to each other to form a rectangular mask. The two plates are placed upon the photograph and each is shifted in relative position until the desired size and shape is obtained. The photograph is then outlined or marked along the inner edges of the mask. The accuracy of this technique in maintaining a desired proportion is approximate at best and is dependent upon the skill and care of the operator. This cropping technique is thus relatively inaccurate and time-consuming.
U.S. Pat. No. 2,246,920 to Kromholz uses a stationary mask with a rectangular window and a moving mask with angled cutting edges. The moving mask is mounted in tracks to guide the sliding of the moving mask relative to the stationary mask. A photograph is placed in the window of the stationary mask. The moving mask is positioned in the tracks to overlap the photograph. Sliding the mask along the tracks over the stationary mask in or parallel to a line diagonal to the apices of an angle of the window of the stationary mask that is opposed to the angle of the cutting edges of the moving mask will alter the size without changing the proportional dimensions of the unmasked area relative to the original area of the window. Thus, while guiding the "L" shaped cutting edges of the moving mask, this device is limited in its ability to crop selected portions of photographs or negatives with separately and independently variable length and width to crop to any desired proportion of length and width.
In a similar manner, U.S. Pat. No. 3,709,591 to Alzman discloses a sheath having two opposite open ends and a centerline intersecting the open ends. A slide is located within the sheath and is of a size and shape complementary to that of the sheath. A centerline of the slide is coincident with the sheath centerline. The slide is adapted to move within the sheath while maintaining coincident centerlines. The sheath and slide each have an identical but irregular quadrilateral aperture therethrough with two diagonally opposed corners located on the centerlines. The two aperture sides forming one of the corners of the aperture are of a different proportion (i.e., different length) than the opposing two aperture sides forming the other corner. The slide aperture is then rotated 180 degrees within the sheath to locate identically proportioned sides of the sheath and slide opposite each other on the coincident centerlines. In operation, the aperture is placed over the selected portion of a photograph and the particular proportion of the selected area is chosen by adjusting the area of the aperture by adjusting the position of the slide one way or the other. If the other cropping proportion is desired instead, then the slide is adjusted in the opposite direction. This device is capable of cropping in two, but only two, different proportions of length to width. Thus, this device is limited in its ability to crop selected portions of photographs or negatives with separately and independently variable length and width to crop to any desired proportion of length and width.
Therefore, a need exists for a simple, easy-to-use device which can be quickly and accurately adjusted to provide any desired size and proportion of window.